The closest system known to the applicant is a system often referred to as "teletext". The teletext system utilises the vertical blanking interval (VBI) of a television transmission for the purposes of broadcasting predetermined blocks of text material. The blocks of text are organised as pages where each page provides one screen of text material. The text format for each page is fixed as are the total number of pages of text material. The pages are broadcast repeatedly consecutively. Noted defects of this kind of system include the rigidity of the text in its page format and also the significant delays that can be encountered whilst a user waits for a requested page to come around to its time for re-transmission.